hola!
Mammals have 4 Chambered heart.
→ Reason :
Mammals have more complex body design in comparision to those of other divisions.
So, they require more pumping of blood to more organs as well as, the heart and body in the case of these animals cannnot afford the intermixing of the bloods (oxygenated and deoxygenated blood).
This is why, mammals have four chambered heart.
Here's a example of Human Heart - [ refer the attachment. ]
→ Deoxygenated blood flows through Right Atrium and Right Ventricle respectively.
→ Oxygenated blood flows through Left Atrium and Left Ventricle respectively.
hope it helps!
